1. Field of the Invention
The present invention relates to a decoding technique for decoding encoded video signals for the purpose of display.
2. Description of the Related Art
The background arts of the present invention include an art described in JP-A No. 134572/2000 and an art described in ISO/IEC 13818-2 (MPEG2 Video) of a non-patent document. In JP-A No. 134572/2000, as a problem to be solved by an invention, an art of “outputting videos, sounds, subpictures, and the like by digital signals to a digital TV receiver from a reproducing apparatus such as a DVD player” is described. A means for solving the problem is described as “A PCM voice signal decoded by a voice decoder 11 is timed in a presentation engine 17, and then is converted into a packet in a PCM/1394 packet conversion part 27. A subpicture decoded in a subpicture decoder 15 is timed in the presentation engine 17, and then is converted into a packet in a 1394 packet conversion part 29. Video PES is converted into TS along with SCR in an MPEG-PS/TS conversion part 25, and is converted into a packet in an MPEG-TS/1394 packet conversion part 31. Each isochronous packet is sent to a digital TV via a link layer 33 and a physical layer 35.” An art for specifying the display position and the display size of an encoded video signal is described in the ISO/IEC 13818-2 (MPEG2 Video).
Recently, a DVD (Digital Versatile Disc) player has come into wide use as a kind of a decoding display device that decodes an encoded video signal for display. The DVD player reads bit streams from a disc in which encoded video signals are stored, and decodes the video signals by a decoder in the player to display the decoded video signals.
In a DVD, a secondary video called a subpicture in addition to a primary video can be reproduced. The secondary video may be closely related to the primary video, and in such a case, it is desirable that the primary video and the secondary video are synchronously displayed. For example, in the above-described JP-A No. 134572/2000, an art for synchronously displaying a primary video and a secondary video is disclosed.
On the other hand, it is preferable that, when a primary video and a secondary video are displayed in combination, the position and the size of the secondary video can be changed according to the contents of the primary video. For example, in FIG. 2A, to avoid a person in a primary video from being hidden by a secondary video, the secondary video is superimposed in an upper right portion. On the other hand, in FIG. 2B, the person in the primary video moves to the right within the video. At this time, if the position of the secondary video is unchanged from that in FIG. 2A, the secondary video would hide the person. Hence, if the display position of the secondary video can be moved to the left as shown in FIG. 2B according to the movement of the person in the primary video, the person would not be hidden.
In the case of this example, since a display position of the secondary video must be specified taking harmony with the primary video into account, it is preferable to provide a system which permits the contents producer of the primary video to specify the display position of the secondary video. In this case, it is preferable that a display position and a display size can be specified on a frame basis. The same is also true for the image size of secondary video.
An art of specifying a display position and a display size of an encoded video signal is disclosed in ISO/IEC 13818-2 (MPEG2 Video). In the art, information of a display position and a display size is inserted in an encoded video signal, and the display position can be specified on a frame basis.
By the way, the contents of such additional information for a secondary video signal such as a display position and a display size are strongly dependent on applications. That is, various types of systems such as different types of storage media including a DVD, and distributions by broadcasting systems and the Internet employ encoded video signals, and in each of the systems, required functions, types of additional information, formats, and transmission methods generally differ.
Hence, if the analysis and extraction of such additional information were performed by hardware, it would be difficult to provide the flexibility to accommodate various applications. If new applications emerge in the future, the hardware will have to be changed to accommodate them, requiring high costs.
On the other hand, if additional information is analyzed and extracted by software, flexibility can be provided, so that it is possible to relatively easily cope with new applications that may emerge in the future. However, processing by software can be slow because of its processing speed, so that the above-described specification on a frame basis may not be guaranteed.
A problem of the present invention is to realize in view of the above circumstances a decoding display device which decodes encoded video signals, which can specify the display position and the display size of secondary videos and the like on a frame basis, and which are flexible in specification method.
An object of the present invention is to solve the problem and provide a decoding apparatus with increased usability.